Schematic and Simulation for a 50mA Current Source/Sink

Hi. I am searching for an expert engineer for providing a valid schematic and verified simulation in TINA-TI for a current source/sink of approx. 50mA over a 1.5kohm load. Load can vary between 300ohm and 1,5k but current has to be fixed and stable. Therefore a Howland Current Pump is required.
Please bid if really expert and with knowledge in the field. Payment will be done after provided and functioning simulation results. A milestone can be assigned after first draft of working circuit. Don't ask for exception. Regards